<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>filer和opacity透明度</title>
    <style media="screen">
      .pdf,img{
        background: url('sky.jpg')  no-repeat;
        width: 500px;
        height: 300px;
        opacity: 0.5;
        filter: alpha(opacity=80);
      }
    </style>
  </head>
  <body>
    <h1>注意：是两张图片的，一张是背景的，天空那张是背景的</h1>
    <div class="pdf">
      <img src="view.jpg" alt="天空">
    </div>
  </body>
</html>
